f only remove the redundant blocker, not all identical blockers

Author: TheBlueMatt

lightning/src/ln/chanmon_update_fail_tests.rs

@@ -3432,8 +3432,7 @@ fn test_reload_mon_update_completion_actions() {
 	do_test_reload_mon_update_completion_actions(false);
 }
 
-#[test]
-fn test_glacial_peer_cant_hang() {
+fn do_test_glacial_peer_cant_hang(hold_chan_a: bool) {
 	// Test that if a peer manages to send an `update_fulfill_htlc` message without a
 	// `commitment_signed`, disconnects, then replays the `update_fulfill_htlc` message it doesn't
 	// result in a channel hang. This was previously broken as the `DuplicateClaim` case wasn't
@@ -3457,13 +3456,19 @@ fn test_glacial_peer_cant_hang() {
 	expect_payment_claimed!(nodes[2], payment_hash, 1_000_000);
 
 	let cs_updates = get_htlc_update_msgs(&nodes[2], &nodes[1].node.get_our_node_id());
+	if hold_chan_a {
+		// The first update will be on the A <-> B channel, which we allow to complete.
+		chanmon_cfgs[1].persister.set_update_ret(ChannelMonitorUpdateStatus::InProgress);
+	}
 	nodes[1].node.handle_update_fulfill_htlc(&nodes[2].node.get_our_node_id(), &cs_updates.update_fulfill_htlcs[0]);
-
 	check_added_monitors(&nodes[1], 1);
-	let bs_updates = get_htlc_update_msgs(&nodes[1], &nodes[0].node.get_our_node_id());
-	nodes[0].node.handle_update_fulfill_htlc(&nodes[1].node.get_our_node_id(), &bs_updates.update_fulfill_htlcs[0]);
-	commitment_signed_dance!(nodes[0], nodes[1], bs_updates.commitment_signed, false);
-	expect_payment_sent!(nodes[0], payment_preimage);
+
+	if !hold_chan_a {
+		let bs_updates = get_htlc_update_msgs(&nodes[1], &nodes[0].node.get_our_node_id());
+		nodes[0].node.handle_update_fulfill_htlc(&nodes[1].node.get_our_node_id(), &bs_updates.update_fulfill_htlcs[0]);
+		commitment_signed_dance!(nodes[0], nodes[1], bs_updates.commitment_signed, false);
+		expect_payment_sent!(&nodes[0], payment_preimage);
+	}
 
 	nodes[1].node.peer_disconnected(&nodes[2].node.get_our_node_id());
 	nodes[2].node.peer_disconnected(&nodes[1].node.get_our_node_id());
@@ -3472,7 +3477,26 @@ fn test_glacial_peer_cant_hang() {
 	reconnect.pending_htlc_claims = (1, 0);
 	reconnect_nodes(reconnect);
 
-	expect_payment_forwarded!(nodes[1], nodes[0], nodes[2], Some(1000), false, false);
+	if !hold_chan_a {
+		expect_payment_forwarded!(nodes[1], nodes[0], nodes[2], Some(1000), false, false);
+		send_payment(&nodes[0], &[&nodes[1], &nodes[2]], 100_000);
+	} else {
+		assert!(nodes[1].node.get_and_clear_pending_events().is_empty());
+		assert!(nodes[1].node.get_and_clear_pending_msg_events().is_empty());
 
-	send_payment(&nodes[0], &[&nodes[1], &nodes[2]], 100_000);
+		let (route, payment_hash_2, _, payment_secret_2) = get_route_and_payment_hash!(&nodes[1], nodes[2], 1_000_000);
+
+		nodes[1].node.send_payment_with_route(&route, payment_hash_2,
+			RecipientOnionFields::secret_only(payment_secret_2), PaymentId(payment_hash_2.0)).unwrap();
+		check_added_monitors(&nodes[1], 0);
+
+		assert!(nodes[1].node.get_and_clear_pending_events().is_empty());
+		assert!(nodes[1].node.get_and_clear_pending_msg_events().is_empty());
+	}
+}
+
+#[test]
+fn test_glacial_peer_cant_hang() {
+	do_test_glacial_peer_cant_hang(false);
+	do_test_glacial_peer_cant_hang(true);
 }

lightning/src/ln/channelmanager.rs

@@ -5485,8 +5485,12 @@ where
 											{
 												let mut found_blocker = false;
 												blockers.retain(|iter| {
+													// Note that we could actually be blocked, in
+													// which case we need to only remove the one
+													// blocker which was added duplicatively.
+													let first_blocker = !found_blocker;
 													if *iter == blocker { found_blocker = true; }
-													*iter != blocker
+													*iter != blocker || !first_blocker
 												});
 												debug_assert!(found_blocker);
 											}